Level Structure in ${\mathrm{Au}}^{197}$ from the Decay of ${\mathrm{Hg}}^{197m}$, ${\mathrm{Hg}}^{197}$, and ${\mathrm{Pt}}^{197}$

Gamma-ray spectra of ${\mathrm{Hg}}^{197}$, ${\mathrm{Hg}}^{197m}$, ${\mathrm{Pt}}^{197}$ were measured with a NaI(Tl) scintillation spectrometer. Electron spectra were obtained with a silicon detector and permanent-magnet spectrographs. Gamma-gamma coincidence measurements were also made. The $K$ internal-conversion coefficient of the 191-keV transition was found to be 0.77±0.2 and 0.93±0.2 by two different techniques. This result is consistent with an $M1\mathrm{}$ transition and does not necessitate any $E0\mathrm{}$ contribution. The energy of the 279-keV transition from ${\mathrm{Hg}}^{197m}$ was found to be (279.5±0.6) keV. The experiments indicate the existence of a 269-keV transition depopulating the 269-keV level in the decay of both ${\mathrm{Pt}}^{197}$ and ${\mathrm{Hg}}^{197}$.